PLC Programming and Automation Guides

Relay Logic vs PLC Logic: Key Differences Explained

Relay logic vs PLC logic: a practical comparison covering speed, flexibility, cost, troubleshooting and when hardwired relays still beat a PLC on the plant floor.

Contactor vs Motor Starter vs Relay: Key Differences

Contactors, motor starters and control relays are often confused but serve distinct roles. This guide breaks down ratings, construction and when to use each one in a control panel.

Relay vs Transistor PLC Outputs: Full Comparison

Relay output vs transistor output on a PLC: pick the wrong one and you'll burn contacts or miss high-speed counts. Here's exactly how they differ and when each wins.

Siemens TIA Portal OB Types: When to Use Each

Organization Blocks control when your Siemens PLC code runs. Learn the OB types, priorities, and exactly when to use OB1, OB30, OB82 and more in TIA Portal.

TIA Portal Function Blocks: FB, DB and Instance Data

Learn how TIA Portal Function Blocks work with Instance Data Blocks, how to pass IN, OUT and IN_OUT parameters, and the real-world gotchas that trip up even experienced S7 programmers.

S7-1200 Diagnostic Buffer: Read Fault Codes Fast

Learn how to read the S7-1200 diagnostic buffer in TIA Portal, decode Siemens fault codes, and fix CPU stops in minutes with a field-tested workflow.

TIA Portal DB Retain and Re-Initialization Explained

Learn how TIA Portal data block retain settings and re-initialization work, why they trip up experienced engineers, and how to get predictable behavior on every power cycle.

Studio 5000 Interview Questions: Real Answers

Preparing for a Studio 5000 or Logix Designer interview? These 15 real questions cover tags, tasks, AOIs, EtherNet/IP, and safety, with field-tested answers.

PLC Programmer Interview Questions: Real Answers

Preparing for a PLC programmer interview? These 30 real questions cover scan cycle, memory, I/O, timers, counters, comms and more, with answers that go beyond textbook definitions.

Allen-Bradley PLC Interview Questions: Real Answers

Preparing for an Allen-Bradley PLC role? These 25 interview questions cover Studio 5000, ControlLogix, tags, EtherNet/IP and ladder logic with concrete, field-tested answers.

4-Wire Proximity Sensor Wiring to a PLC

A 4-wire proximity sensor gives you both a NO and NC output from one body. Learn exactly how to wire each output type to your PLC input module, with real gotchas.

Photoelectric Sensors: Types, Wiring and PLC Use

Learn how photoelectric sensors work, how to wire them to a PLC input, and when to choose through-beam vs diffuse vs retro-reflective mode. Real field gotchas included.

Proximity Sensor Wiring to a PLC: Full Guide

Learn how to wire 2-wire, 3-wire and 4-wire proximity sensors to a PLC input. Covers PNP and NPN types, color codes, sinking vs sourcing inputs, and common wiring mistakes.

Inductive vs Capacitive Proximity Sensors: Full Guide

Inductive and capacitive proximity sensors look identical but detect completely different targets. Learn the key differences, typical specs, and wiring rules for PLC integration.

NPN vs PNP Sensors: Wiring and PLC Connection

NPN and PNP sensors switch current in opposite directions. Get the wrong one for your PLC input card and the signal never works. Here is how to tell them apart and wire each type correctly.

DIN Rail Terminal Blocks: Wiring and Selection Guide

DIN rail terminal blocks are the backbone of every control panel. This guide covers types, sizing, torque specs, jumper use, and common wiring mistakes that cause real field problems.

PLC Panel Electrical Noise: Causes and Fixes

Electrical noise in PLC panels causes phantom inputs, drifting analog readings and comm errors. Learn the real causes and practical fixes, wiring changes included.

PLC Output Wiring: Relay, Transistor and Triac

Relay, transistor and triac PLC outputs wire differently and fail differently. Here is exactly how to connect each type and avoid the mistakes that kill modules.

PLC Analog Output Wiring: 4-20 mA and 0-10 V

Step-by-step guide to wiring PLC analog outputs: 4-20 mA current loops and 0-10 V voltage signals, with real wiring gotchas, load limits and field-verified tips.

PLC Counter Reset: 4 Methods and When to Use Each

Resetting a PLC counter sounds simple until it bites you mid-batch. This guide covers every reset method, when each one is right, and the gotchas that cause missed counts.

PLC Counter Preset vs Accumulator: What Each Does

The preset and accumulator in a PLC counter do very different jobs. This guide explains each one, how they interact, and the real-world gotchas you need to know.

CTU vs CTD: PLC Counter Instructions Compared

CTU counts up from zero; CTD counts down from a preset. Learn when to use each, how they differ across platforms, and how to wire both into working ladder logic.

Cascading PLC Timers: Chain TON Logic Right

Learn how to cascade TON timers in PLC ladder logic to build reliable multi-step timed sequences. Real examples, common mistakes, and field-tested patterns.